go: upgrade to maxminddb-golang/v2

[mm-ipinfo]

This upgrades to maxminddb-golang v2. See https://github.com/oschwald/maxminddb-golang/blob/main/MIGRATION.md for the differences.

This is mainly to make advantage of the new reader API to improve the export path in a subsequent PR (10x performance improvement on JSON export; #48).

$ go test ./...
?   	github.com/ipinfo/mmdbctl	[no test files]
ok  	github.com/ipinfo/mmdbctl/lib	(cached)

[max-ipinfo]

No sure if you need similar handling still

[mm-ipinfo]

Not needed anymore, the error is now embedded in the result struct. If there is an error it will raise at decode time.

[max-ipinfo]

The migration docs (https://github.com/oschwald/maxminddb-golang/blob/main/MIGRATION.md) mention:

Options such as SkipAliasedNetworks now use an options pattern. Pass them as Networks(SkipAliasedNetworks()) or NetworksWithin(prefix, SkipEmptyValues())

[mm-ipinfo]

Sorry forgot to mention that. The option is now the default and has been replaced by the opposite IncludeAliasedNetworks option. So no need to pass it anymore. The doc is probably out of date 🙂

This was introduced in this commit: oschwald/maxminddb-golang@4a5a9d6